A week with an iPad has shown me how poor presentations and other documents get rendered on a PC (or a Mac). Leaving the touch screen aside, and even for a PDF viewer, navigating between pages is incredibly slow and the borders of the screen are packed with distracting menus.
Maybe this can all be brought back to the roots of these applications: they were designed for editing text line by line, changing data cell by cell. Each page is built up real time from its components. Editable text gets pet in the right font, the right size, aligned, images are scaled to the right size, colors added. All this takes processing time. The iPad (I think) converts the whole document to some sort of image and caches this image into memory. The result is lightning fast scrolling between pages in a document.
There is no reason why this cannot be implemented on a PC/Mac as well. It is bit like the revolution of the Firefox and Google Chrome browsers that were specifically designed to render content as quickly as possible.